NL8000984A - Blow molding device for hollow duplex holders. - Google Patents

Description

P & c W 5272-6 Ned.

Blow molding device for hollow duplex holders

The invention relates to an improved injection molding device with which moldings of plastic for duplex containers with bottom can be formed and can be stretched and blow molded in the form of hollow molded articles in a continuous manner.

When an injection molded plastic molding with bottom is placed on a core in a blow mold, for the purpose of blowing air out of the core to bring the molding into the shape of a hollow object, it is technically possible to use a so-called duplex molding or a double-layered molding of wall and bottom and deforming it by blow molding, since the core can be used as a transfer member for this molding. However, when the hollow articles are to be made of an injection molded molding with bottom, by heating and stretching this molding, the core used in the injection molding can be used to form the first wall layer of the molding with bottom, but not for the second wall layer, ie not without changes, since the molding is clamped in a neck shape, which must also be transferred to the further stage. Each step of the steps to be performed, namely injection molding, heating, stretch blow molding and mold release, must be performed each time while the intermittent rotary movement of the molding machine is stopped. It is impossible to use another molding cycle just before injection molding. Therefore, an apparatus of the kind in which the neck shape is transferred between the stations together with a molding by an intermittently rotating transfer plate is not suitable for the manufacture of hollow articles 25 with double layer thickness.

However, such a molding device can still be used for the manufacture of duplex containers when a double molding injection molding device is included in the molding cycle of the injection molding steps to the mold release.

The known molding devices of this kind of the so-called four-stage type with four neck shapes, which has four work stations, i.e. an injection molding station, a heating station, a stretch blow molding station and a unloading station. Thereby, a transfer plate is rotated intermittently about a support axis and this plate is stationary in said order to perform the respective steps when the neck shape is stationary in each station. In order to obtain duplex holders and firstly duplex moldings with bottom, an injection molding device is used in which a cold molding, which has been formed by injection molding, is attached 800 0 9 84 -2- to the core as an inner molding, after which a outer molding by injection molding must be applied outside and around the inner molding.

However, special members are then required to attach the cold molding to the core. In addition, excellent quality hollow duplex articles are not produced when molten material is applied to a cold molding.

Based on the prior art four stage molding apparatus having four neck shapes, which are stationary consecutively at each station, the invention provides a new injection molding section capable of continuously producing duplex moldings 10 with bottom, after which duplex holders are obtained with a molding cycle similar to that which is used in forming single wall thickness containers.

Four stages are required for molding: injection molding, heating, stretch blow molding and mold release. However, the number of neck shapes need not be equal to the number of stages since each neck shape remains stationary in each station.

Therefore, the invention provides an apparatus of the said four-stage type in which the injection molding station is enlarged and includes stop positions for two neck shapes, with each neck shape stationary at each stop station.

As a result, two neck molds are always stationary in the injection molding station, so that each neck mold is stationary twice in the injection molding station, so that a duplex molding can be formed with bottom, only by injection molding. Furthermore, two pairs of molds can be opened and closed by a common clamping device or by separate clamping devices. The intermittent rotation of the transfer plate is performed at smaller angles than with the four-necked device, but this does not detract from the molding cycle.

With the device according to the invention, it is possible to continuously manufacture duplex containers and other hollow molded articles, in a similar manner as when single wall thickness and bottom moldings are injection molded and further blow molded, in a four-stage, four-neck apparatus . Both pairs of injection molds can be opened and closed simultaneously or separately, depending on the plastics used. It is possible to manufacture the duplex holders with a single type of plastic, but also with two different types of plastic. By suitable selection of the plastics, it is possible to mass-produce objects which are stronger and more airtight than the usual duplex containers.

The invention will be explained in more detail below with reference to the drawing, which shows three embodiments of devices according to the invention.

Fig. 1 shows vertical sections or of an inner molding (A ^), a duplex molding with bottom (A ^) and a duplex holder (C).

FIG. 2 is a top view of the device.

Fig. 3 is a vertical section according to III-III of FIG. 2.

Fig. 4 is a vertical section through the heating station.

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Fig. 5 is a vertical section through the stretch blow molding station.

Fig. 6 is a vertical section through the unloading station.

FIG. 7 is a vertical section through another embodiment at the injection molding station.

Fig. 8 is a top view of a third embodiment at the location of the injection molds.

Fig. 1 (A ^), (A ^) and (C) show a duplex molding 1 with bottom 15 and a hollow shaped object, respectively, obtained by stretching and blow molding, here a duplex bottle 2. The inner molding with 1a, the outer mold with 1b, the inner layer of the bottle with 2a and the outer layer with 2b.

In Fig. 2 and following, the molding device 10 is shown, which 20 has a horizontal lower base plate 12 mounted on a machine base 11 and an upper base plate 13 located above the lower base plate and parallel thereto at a certain distance. The distance between these plates represents the shape space.

The upper base plate 13 is horizontally attached to the machine base by two tie rods 9 mounted vertically on the base adjacent to the injection molding station, parallel to and spaced apart, with support members (not shown) mounted in the rack. blow molding station C.

A transfer plate 16 is mounted below the bottom surface of the upper base plate 13 and is intermittently drivable by a motor 15 at an angle of 72 ° about a central support shaft 14. Five neck shapes 17, closed by springs 17a, are mounted on the bottom surface of the transfer plates 16 and are equidistant from each other, whereby they can be opened and closed radially. Each neck mold 17 has a standstill 35 in the four molding workstations, i.e., the injection molding station A, the heating station B, the stretch blow molding station C and the station D for unloading. form.

Among the 2nd stations, the injection molding station A has the stop positions for two neck molds, while each of the other stations is located at 800 0 9 84 -4- location of one neck mold 17.

Fig. 3 shows the injection molding station A, in which a spark clamping device 18 is arranged vertically above the top base plate 13.

Two pairs of injection molds 21, 22, one for each neck mold 17, are mounted on a lower mold clamping plate 19 and form a first mold and a second mold A 1, respectively. Cores 23, 24 of the same shape are arranged under the top mold clamping plate 20 and protrude through spaces in the top base plate 13, the transfer plate 16 and the neck shapes 17.

In the injection molding station A, when each neck mold is stationary above the injection molds 21, 22, these molds are closed by a mold clamp cylinder 25, together with the neck molds 17. Thereafter, the cores 23, 24 are introduced into the mold cavities by the mold clamp cylinder 26. When the molds are closed and clamped tightly, injection molding devices 29, 30 with a nozzle pressed against the mold supply the molten material 15. Thereby, the inner molding is formed around the core 23 in the first mold A ^ and the outer mold lb in the second mold A ^, thereby creating a duplex molding 1. In this case, in the first mold A ^, the molten material is pressed into the neck mold 17, thereby also forming the threaded portion on the neck, as shown in Fig. 1 (A ^). In the second form A2, material has already filled the neck form and no new material enters the neck form at the location of the screw thread, but only the outer molding is formed outside the inner molding 1a, as indicated in Fig. 1.

After the injection molding, the mold is opened and the cores 23, 24 are removed from the inner molding 1a and the duplex molding 1, after which the two molding pieces are clamped by the neck molds 17. When the transfer plate 16 is now rotated, the inner molding 1a is its neck shape 17 is transferred to the second shape A ^ and the duplex molding 1 is transferred to the heating station B.

It can be seen from Fig. 4 that the duplex molding in the heating station B is heated in an oven 31 above the lower base plate 12. After the correct temperature has been reached, the duplex molding is transferred from the transfer plate after another partial rotation. stretch blow molding station C according to Fig. 5.

The stretch blow molding station C has a blow mold 32 on the lower base plate 12, which can be opened and closed in the radial direction, while a nozzle 33 is inserted into the molding through the upper base plate 13, together with a draw bar 34. After the mold is closed, the molding is axially stretched by the strain rod 34 by means of air cylinders 35, 36 applied to the top base plate 13 and the molding is stretched in the radial direction along the wall of the blow mold with air, which is supplied through the nozzle 33. Herein, the duplex bottle 2 according to Fig. 1 (C) is formed, with an inner layer 2a and an outer layer 2b.

After the stretch blow molding, the mold is opened and the duplex bottle 2, held by the neck shape, is transferred to the unloading station D through the plate 16.

In the station 2, a guide rod 37 is shaped 10 by means of an air cylinder 38, through the top base plate 13 and the transfer plate 16, into the mouth of the bottle held by the neck shape 17. After insertion of the guide bar, the neck shape 17 is opened and the bottle 2 drops vertically down, guided by the guide bar 37, the bottle not sticking to the halves of the opened neck shape 15.

When the transfer plate 16 now performs a further partial rotation, the neck mold 17 is closed and transferred to the first mold A ^ of the injection molding station A, after which a subsequent series of operations begins.

In the embodiment of Fig. 7, a separate mold clamping-20 mechanism is provided for the first mold A ^ and for the second mold A ^ of the injection molding station A. Parts corresponding to those of Fig. 2 are indicated by the same reference numerals and are not further described.

A tie rod 91 is arranged vertically in the center of the injection molding station A, ie centered between the tie rods 9. In the first form, a lower mold clamping plate 91 and an upper mold clamping plate 201 are vertically movable between the rod 91 and the outer tie rod. 9. In the second mold, a lower mold clamping plate 192 and an upper mold clamping plate 202 are arranged between the central pull rod 91 and the outer pull rod 9, in a similar manner. Oil-operated hydraulic piston-cylinder units have pistons 271, 272 in cylinders 251, 252, the pistons being attached to the lower ends of the tie rods 9 and 9, respectively. 91 which are connected to the lower clamping plates 191 and 192 so that the molds can be clamped separately.

Likewise, oil-operated hydraulic piston-cylinder units 35 are provided, with pistons 281, 282 in cylinders 261, 262, the pistons of which are attached to the upper ends of said tie rods, which are connected to the upper mold clamping plates 201, 202, whereby the molds can also be clamped separately, such as the plates 191, 192.

The advantage of the separate shape clamping mechanisms for the 800 0 9 84-6 first mold A and the second mold, respectively, is that the hardening time can now be selected as desired, depending on the type of plastic used, so that duplex holders can be made of two different synthetic resins.

Pig. 8 shows yet another embodiment of the device, in which engagement parts 21a, 22a for the injection molding nozzles protrude from the outer side surfaces of the two pairs of injection molds. These side surfaces run in different directions, but the engaging parts are shaped such that the projecting ends thereof run in the same direction, so that the two injection molding devices 38, 39 can work parallel to each other, which facilitates the pressing of the nozzles.

In summary, according to the invention, the injection molding station A comprises the stop positions for two neck molds 17 and are two pairs of injection molds. 21, 22 respectively arranged for each neck shape 17, so that they can be opened and closed separately. The first form A ^ is next to the second form A ^. At each standstill of the transfer plate 16, an inner molding 1a and an outer molding 1b are simultaneously injection molded to form a duplex container. Obviously, the invention is not necessarily limited to the formation of duplex objects. Three-layer moldings can also be manufactured by increasing the number of neck shapes and expanding the injection molding station to three stop positions for three neck shapes.

800 0 9 84

Claims (4)

1. Blow molding device for forming two-walled articles, so-called duplex articles, which device comprises a transfer plate, arranged horizontally above a machine base and comprising a number of neck-5 shapes, equally spaced on the bottom surface, of drive members for intermittently driving the transfer plate in a horizontal direction, of four workstations, namely an injection molding station, a heating station, a stretch blow molding station and a unloading station, each at a stop position of the neck molds per the machine base, characterized in that the number of neck molds is one greater iS. then 10 is the number of work stations at which the injection molding station is expanded and includes the stop positions for two adjacent neck molds, while the injection molding station has two pairs of injection molds, for separately forming an inner molding and an outer molding, which, in conjunction with through the neck molds, in the stop positions from two adjacent neck shapes 15 cores inserted a duplex molding with bottom can be formed- 2. Blow molding device according to claim 1, characterized by a transfer plate, which is rotatable intermittently through a constant angular distance, which transfer plate is situated against the bottom surface of an upper base plate, which is horizontally supported above the machine base, by a pair of tie rods for supporting of the top base plate, and by mold clamping mechanisms mounted above and below the top base plate, simultaneously mounting an upper mold clamp plate and a lower mold clamp plate vertically movable along the tie rods. 3. Device according to claim 1, characterized in that a further tie rod is arranged vertically between the two tie rods for supporting the top base plate, two pairs of top mold clamping plates and bottom mold clamping plates being separately mounted between the central tie rod and the outer tie rods and are vertically movable such that the two pairs of injection molds in the injection molding station 30 can be opened and closed separately. Device according to claim 1, characterized in that engaging parts for the injection molding nozzles protrude from each outer surface of the two pairs of injection molds, such that the two injection molding devices can be arranged parallel to each other. 80 0 0 9 84 '